DescriptionThis dissertation considers how we should treat human beings whose moral status is controversial, such as human embryos, fetuses, and the irreversibly comatose. My approach to this question sidesteps the traditional “personhood” debate, and instead explores the issue of moral status through the lens of what Judith Jarvis Thomson calls personal ontology—the branch of metaphysics that asks what kind of being we are and what the conditions of our identity over time are. Instead of asking what properties something must exemplify in order to count as a person, personal ontology is concerned with the kinds of things that might exemplify those properties, such as immaterial souls, human animals, embodied minds, bundles of perceptions, etc. One of my central claims is that we are not human animals—beings that persist through time in virtue of the continuity of purely animal functions such as respiration, circulation, and digestion. Instead, I argue, we are conscious beings distinct from human animals, and our continued existence, under normal conditions, depends on the continuity of our neural capacities for consciousness. I argue that this view supports several important conclusions, including the conclusion that killing a human animal and/or using it as a biological resource is morally justified if this is the only reasonable way to achieve a certain significant good—the fulfillment of a sufficiently weighty self-interest that we have--and it does not violate anyone else’s rights or produce any evil that nullifies or outweighs this good.